The present invention is directed to an improved acoustic resonator apparatus, and more particularly to an acoustic resonator apparatus for efficiently transmitting of acoustic energy from a plurality of acoustic transducer means to a fluid passing through a cylindrical shell.
It has been known for some time that agitation of a fluid by sonic or supersonic means produces desirable changes in the fluid. For example, among such desirable changes are destruction of bacteria, mixing ordinarily immiscible compounds, treating metals in their molten state to change crystal structure, and rapidly homogenizing liquids.
One method of attaining agitation has been to mount a plurality of acoustic transducers on a cylindrical shell, and pass the fluid through the shell. For example, U.S. Pat. No. 2,578,505 illustrates a prior art apparatus in cylindrical shell configuration while U.S. Pat. Nos. 3,761,732 and 4,139,806 disclose other acoustic resonating configurations.
As can be appreciated, it is desired to couple the acoustic energy to the medium in the shell as efficiently as possible. Prior art cylindrical shell resonators have used the monoaxial transmission method wherein transmission is accomplished by positioning transducers radially around the shell in an evenly distributed manner and operating all transducers in phase at a set frequency.
The main disadvantages of this approach are that the vibration transmission is partially cancelled by other vibration transmission in the shell due to longitudinal and radial wavelength mis-match and, since a cylindrical shell has its maximum resistance to deformation when pressure is applied uniformly about its circumference, when evenly spaced transducers are operated in phase, the uniformly applied pressure results in internal stresses and strains in the resonator, which negate a large portion of the acoustic transmission.
It is thus the principal object of the present invention to provide an apparatus for more efficiently transmitting acoustic energy from a plurality of acoustic transducer means to a medium passing through a cylindrical shell.
In accordance with the invention, the above object is accomplished by providing a cylindrical shell for containing a medium passing therethrough, and disposing a plurality of pairs of associated acoustic transducer means on the shell, with each pair being comprised of two transducer means 180.degree. displaced from each other, and each pair being displaced 90.degree. on the shell from its associated pair. Each pair of acoustic transducer means is excited with energy of the same frequency and magnitude as its associated pair but 180.degree. displaced in phase. The result is eccentric deformation of the shell and efficient coupling of energy from the transducer means to the medium.